Your most indispensable "tweak"?


Trying to narrow my possibilities down... 
redwoodaudio
Hey All,

Over the counter...inexpensive...effective for wax "producers" ...better than having "dry ears" btw.  https://www.debrox.com/

For the more adventurous:  http://marigoaudio.com/the-audiophile-voice/
Controversial, but do some research...I have just completed a full dot application of my Music Reference RM-10 MKII.  Here is how I shared results with my audio buds:

"25 years ago, my local Tech (Rick), now retired to Florida, was doing deep dive experiments around resonances, macro and micro, including electrical resistances. He possessed the technical and listening skills...plus the extreme patience to become expert in applying the VTS Dots. Yes, you can harm the sound, easily reversible. He referred to it as "opening up the sound," probably the most apt description.  
So, what's my result? Bloom was the first thing that came to mind. A maturation of the system. Clarity and greater honesty of the timing of events, like live. Less congestion of massed instruments and chorus with an enhanced sense of space and time, enhancing the holographic ability associated with great tube playback.
It's not by chance that the esoteric high end is finally paying extreme attention to floating circuit boards, extreme isolation racks, layered and exotic materials for loudspeaker enclosures and feet. Turntable designs are off the charts identifying and addressing plinth, arm, headshell and stylus resonances
It is a shame that these lightweight, layered music makers have been largely ignored by our industry. Proof's in the pudding."

More Peace, Pin
So I picked up a novum pmr premium resonator on the basis of a recommendation in this thread (and other reviews) and the effect it has in my room is beautiful. Hard to describe, but improves tonality, image density, without any negatives. It's also quite beautiful to look at sculptural. I've since found a second one used and am waiting to receive it. Definitely got me more open minded about "tweaks". Love all the ideas here. 
I have to second the Critical Mass footers.
I put a set of 4 of the 1.0 under my Lumin X1 and I am wowed. 
I then ordered 2 more sets for my mono block amps. 

ozzy
I like  sandthemall  basic suggestion. Dedicated 10 gauge wire (shielded) and hospital grade outlets.